Just had a quick look at both. Here's what I found:
direnv
* looks for a .envrc file
* starts a subshell
* loads environment variables into the subshell from the .envrc file
autoenv
* looks for a .env file
* executes commands from that file in the current shell
* allows cleanup via a .env.leave file
This seems quite an unfortunate state of affairs to me because:
* my .env files usually just contain environment variable declarations
* a .envrc seems much more non-standard and based on the name alone I might expect it to be executed (like .bashrc)
Is there any way to configure these to swap the filename conventions?